Work is now underway with riboflavin-binding proteins and the riboflavin-5'-phosphate-dependent pyridoxamine (pyridoxine) 5'-phosphate oxidase; in short order, purification and properties of FAD synthase from mammalian tissue will be started. The diversity of riboflavin-binding proteins is being investigated for several species, and the more complete characterization of those in human plasma will be done. Completion of studies delineating the active-site amino acid residues of pyridoxamine oxidase will include chemical modification of Arg-Lys involved in coenzyme and substrate/product binding. Fast-reaction measurements are being considered to examine the on-off rate constants involved in the catalytic mechanism. As only crude preparations of FAD synthase have heretofore been available for study, the enzyme from liver will be purified to homogeneity prior to a thorough investigation of its properties.